Simple or unicameral bone cysts are metaphyseal lesions of long bones. They usually move away from the physis with growth to become diaphyseal in location. Involvement of the physis and epiphysis by these cystic lesions is very rare. This paper reports a case of simple bone cyst of the proximal humerus in a 11-year-old girl which was shown by MR imaging to extend through the physis into the epiphysis.